Plaquenil, or hydroxychloroquine, and its related compound chloroquine, has long been identified to be associated with a retinal toxicity. This toxicity occurs rarely (in the range of 0.5-3.5% of patients on the drug), but, nevertheless, it remains a concern as the toxicity to the retina is mostly, if not wholly, irreversible and the visual sequelae from this toxicity can be devastating. A relationship has been proposed between mutations in the ABCA4 gene and the development of Plaquenil toxicity. If a relationship between ABCA4 mutations, or other genetic mutations, and Plaquenil toxicity is identified this would enable the practice of personalized medicine. The practice of personalized medicine is supported by a bill from the US congress and utilizes the knowledge gained by genetic sequencing to tailor an individuals medical care. It would follow that patients considered for hydroxychloroquine or chloroquine therapy undergo genetic screening for genetic mutations, such as ABCA4 mutations, so that patients who would be exquisitely sensitive to toxic effects of this drug are identified before the treatment is implemented. The objective of this study is to identify genetic mutations, starting with an analysis of ABCA4 mutations, that may be correlated with Plaquenil toxicity and correlate these with the participants phenotypes. This study will recruit 30 patients with Plaquenil-induced retinal toxicity and at least 60 control participants to participate in this study. This is an observational study that requires 1-2 outpatient visits to the NIH Clinical Center or a local ophthalmologists office over a period of time convenient to the participants, not to exceed two years. After gathering a complete medical, family and surgical history, participants will have standard physical and eye examination. The eye examination will include a dilated fundus examination. Non-invasive ophthalmologic testing (e.g., visual field testing, OCT, photos, and autofluorescence) may be performed. Photographs (ophthalmic) will be taken to document the Plaquenil toxicity. Participants will have a 30 cc blood sample drawn for genetic analysis. During this fiscal year, the protocol has gained IRB-approval and recruitment of patients has started. An electronic medical record form has been developed and utilized to store clinical data collected as part of this protocol. The collaboration with Dr. Ayyagaris lab at University of California San Diego will provide the expertise in sequencing and determining the significance of any mutations detected in the patients DNA samples. We have enrolled participants and continue to enroll participants into this study at the NEI.